JP2005086392A - Optical space communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an optical space communication device which is low in cost, small in size and light in weight, and can correct the deviation of an optical axis at high speed. <P>SOLUTION: An optical system is separated to a collimate optical system and a separation optical system 11, which is movable independently from the collimate optical system. Peripheral circuits of a light emitting element such as LD and a light receiving element such as an APD are placed at a different place, and connected with the separation optical system through an optical fiber or a minimum cord or cable to drive the separation optical system at high speed with small force. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is an optical space communication device that communicates by transmitting an optical signal by a light beam propagating in free space, which is installed oppositely between two distant points, and in particular, an optical axis correction function of a light beam due to an angle deviation of the device It relates to a device having

  In general, an optical space communication device that performs communication by propagating a light beam in free space needs to transmit with a narrow light beam with a light beam divergence angle as small as possible in order to transmit light power efficiently. is there. However, if the light beam is narrowed, the light beam is likely to be detached from the counterpart device due to the fluctuation of the angle of the building or installation base due to wind pressure or vibration, distortion due to temperature fluctuation, etc., and stable communication is difficult. Therefore, as shown in FIG. 4, an apparatus having an optical axis deviation correction function is devised that performs tracking control so that the light beam always faces the other apparatus by correcting the angle change even if the angle of the apparatus changes ( For example, refer to JP2001-111491).

  FIG. 4 shows one side of a pair of opposing devices. In FIG. 4, 20 is an optical system for transmitting / receiving a light beam. An optical signal transmitted to the counterpart device is emitted from a light emitting element 21 such as a semiconductor laser. The light of the semiconductor laser is polarized, and the polarization direction is set to be horizontal to the paper surface. The polarized light in this direction is reflected by the polarization beam splitter 22 in the direction of the light transmitting / receiving lens 23, and the light transmitting / receiving lens 23 transmits a light beam 24 of a substantially parallel light beam having a slight spread to the direction of the counterpart device. . Since the light emitting element 21 is normally modulated with a high-speed signal, the light emitting element 21 is mounted in a shielded case together with a modulation circuit and modularized in order to prevent noise generation.

  On the other hand, the light transmitted from the counterpart device follows the reverse path on the same optical axis as the transmission optical signal from the own device and enters the polarization beam splitter 22 from the transmission / reception lens 23, but is received from the counterpart device. Since the light is set so that the polarization direction is orthogonal to the transmission light (the polarization direction is perpendicular to the paper surface), the light passes through the polarization beam splitter 22 as it is and enters the beam splitter 25. Most of the received light is reflected by the beam splitter 25 and enters the light receiving element 26 for detecting an optical signal, and a communication signal is detected. Since the light receiving element 26 normally handles weak and high-speed received signals, the light receiving element 26 is mounted in a shielded case together with a signal amplification circuit and modularized in order to prevent the influence of external noise.

  On the other hand, part of the light that is not reflected by the beam splitter 25 passes through the beam splitter 25 and enters the optical position detection element 27.

  The optical position detection element 27 is a photodiode divided into four as shown in FIG. 5, for example. FIG. 5 shows a state in which the light spot 42 hits the photodiode divided into four parts 27a to 27d. The position of the light spot 42 can be known by comparing the outputs of the four photodiodes 27a to 27d. The signal from the optical position detection element 27 is processed by the control circuit 28 as angle correction information, and a drive signal is output to the drive circuit 29 of the optical system 10. Then, the drive circuit 29 moves the vertical drive mechanism 30 and the horizontal drive mechanism 31 so that the position of the light spot 42 comes to the center of the light position detecting element 27, and the outputs of the four photodiodes 27a to 27d are output. The angle of the optical system 10 is driven and controlled in such a direction that they are all equal.

  In the optical system 10, the optical position detection element 27, the light emitting element 21, and the optical signal detection light receiving element 26 are all adjusted in position so that the optical axes coincide with each other, and a light spot is formed at the center of the optical position detection element 27. In the state of being hit, light is also incident on the center of the light receiving element 26 for detecting an optical signal, and the center of the light from the light emitting element 21 is radiated in the direction of the counterpart device.

  In this way, optical axis deviation correction is performed by tracking control so that the transmitted light always becomes the direction of the received light, that is, the direction of the counterpart device.

  As another conventional embodiment, there is one having a mechanism for deflecting light inside the optical system 20 instead of performing optical axis deviation correction by driving the optical system itself. For example, as shown in FIG. 6, the drive circuit 29 drives the angles of the horizontal deflection mirror 32 and the vertical deflection mirror 33 to deflect the light within the lens barrel, thereby correcting the optical axis deviation.

As another conventional embodiment, FIG. 7 uses a so-called lens shift optical system 38 in which the lens shifts in a direction perpendicular to the optical axis as means for correcting the optical axis deviation. In FIG. 7, the movement in the horizontal direction is depicted on the paper surface, but in actuality, the lens is freely shifted in two dimensions in the horizontal direction and the vertical direction on the paper surface, and the light beam 24 is deflected in accordance with the shift amount of the lens. As a driving means for lens shift, an actuator using a voice coil, a linear motor, or the like can be used.
JP 2001-111491 A

  In the above two conventional examples, even if the angle of the apparatus is changed, stable communication can be performed even when the light beam divergence angle is reduced by correcting the optical axis deviation. There is.

  The method of having a drive mechanism outside the optical system as in the example of FIG. 4 and changing the angle of the entire optical system can freely take a wide variable range of angles, and can cope with large angular fluctuations. Since a large object is driven, it is difficult to move the angle at a high speed, and it is impossible to respond to a fast angular fluctuation.

  Further, in the system having a mechanism for deflecting light inside the optical system as in the examples of FIGS. 6 and 7, it is relatively easy to change the angle of the light at high speed, so that it responds to a fast speed angle change. However, in the example of FIG. 6, a space for the part to be folded back by the mirror is required, the entire optical system becomes large, the apparatus becomes large, the handling is inconvenient, and the cost increases. Also, since the mirror is required to have high surface accuracy, the cost also increases in this respect. In the example of FIG. 7, a special optical system that changes the direction of the light beam by driving a lens in the middle of the optical path is used. Therefore, when trying to obtain a certain angle variable range, aberration correction of the lens and change in the angle of the light beam are performed. A special design for increasing the size is required, and the number of lenses is increased (the number of lenses is illustrated as being smaller than the actual number because FIG. 7 is a principle explanatory diagram), and the cost increases.

In order to solve the above problems, to achieve a compact and lightweight optical space communication device that performs optical axis misalignment correction at high speed at a low cost,
A first invention according to the present application is an optical space communication device that is installed facing each other and communicates by a light beam, and converts a divergent light beam into a light beam that is a substantially parallel light beam and transmits the light beam to a counterpart device. And a first optical system (collimating optical system) for receiving a light beam that is a substantially parallel light beam from the counterpart device and converting it into a convergent light beam,
A second optical system (separation optical system) for separating the light beam sent to the counterpart device and the light beam received from the counterpart device, each on the same optical axis and in opposite directions;
It is characterized by having means for changing the relative position of the second optical system with respect to the first optical system (including not only translation but also angle change).

In addition, a second invention related to the present application is an optical space communication device that is opposedly installed between distant points and performs communication using a light beam.
A first optical system for converting a divergent light beam into a light beam that is a substantially parallel light beam and sending it to a counterpart device, and for receiving a light beam that is a substantially parallel light beam from the counterpart device and converting it into a convergent light beam When,
A second optical system for separating the luminous flux sent to the counterpart device and the luminous flux received from the counterpart device, each on the same optical axis and in opposite directions;
Drive means for changing the relative position of the second optical system with respect to the first optical system (including not only translation but also angular change);
Angle detection means attached to the second optical system for detecting the angle of the light beam received from the counterpart device;
Based on the information from the angle detection means, the light beam transmitted to the counterpart apparatus is always controlled by controlling the drive means so that the angle of the light beam received from the counterpart apparatus becomes a predetermined value. It is characterized by having control means for tracking control so as to go in the direction.

  A third invention according to the present application has a light emitting element for generating an optical signal to be sent to a counterpart device, which is in a place different from the second optical system. The two optical systems are connected by an optical waveguide (optical fiber, light guide, etc.), and the transmission light from the light emitting element is guided to the second optical system by the optical waveguide.

  According to a fourth aspect of the present invention, the second optical system has an optical signal detection element for detecting an optical signal included in the light beam received from the counterpart device, and is detected by the optical signal detection element. The circuit for amplifying the electrical signal is placed at a location different from the second optical system.

  Further, a fifth invention according to the present application has an optical signal detection element for detecting an optical signal received from a counterpart device, which is in a place different from the second optical system, and this optical signal. The detection element and the second optical system are connected by an optical waveguide (optical fiber, light guide, etc.), and the received light from the second optical system is guided to the optical signal detection element by the optical waveguide. And

  According to a sixth aspect of the present invention, the second optical system includes a light emitting element for generating a light beam including an optical signal transmitted to the counterpart device, and a circuit for controlling the light emission intensity of the light emitting element. And a circuit that modulates the light-emitting element in order to generate an optical signal is placed at a location different from the second optical system.

As described above, according to the present invention, in an optical space communication device that is installed oppositely between remote points and performs communication using a light beam,
A separation optical system 11 that is compact and lightweight is separated from the collimating optical system 10, and a peripheral circuit of a light emitting element such as an LD or a light receiving element such as an APD is also placed in another location, and an optical fiber is formed between the optical system and the separation optical system 11. Alternatively, the separation optical system 11 can be driven at a high speed with a light force by connecting with a minimum of cords and cables. As a result, it is possible to realize a small and light optical space transmission apparatus that performs optical axis misalignment correction at high speed while being low in cost.

(First embodiment)
FIG. 1 shows an optical space transmission device having an optical axis deviation correction function according to the present invention. Each number on FIG. 1 indicates a component having the same function as the number in FIGS. In the embodiment of FIG. 1, the optical system that transmits and receives light is separated into a collimating optical system 10 that is a first optical system and a separating optical system 11 that is a second optical system. Are movable independently of the collimating optical system 10. Further, the separation optical system 11 is gathered in a small size and moves with a light force.

  A light emitting element 21 such as a laser diode (LD) is placed near a light emission control circuit or a modulation circuit on a printed circuit board or the like at a location different from the separation optical system 11. Light including an optical signal from the light emitting element 21 is transmitted to the separation optical system 11 by the transmission optical fiber (or light guide) 14 and is directed to the polarization beam splitter 22 from the end face of the optical fiber fixed to the separation optical system 11. Emitted.

  4 to 7, the light is reflected by the polarization beam splitter 22, exits the separation optical system 11, and proceeds in the direction of the collimating optical system 10. Then, the collimating optical system 10 transmits an almost parallel light beam 24 having a slight spread in the direction of the counterpart device.

  Since the light emitted from the end face of the optical fiber is not polarized, the polarizing element 09 is inserted in front of the polarizing beam splitter 22 to be polarized, and then reflected by the polarizing beam splitter 22.

  On the other hand, the light transmitted from the other apparatus follows a reverse path on the same optical axis as the transmission optical signal from the own apparatus, enters the collimating optical system 10, converges, and enters the polarization beam splitter 22. The subsequent path is the same as that of the conventional embodiment shown in FIGS. 4 to 7. The received light from the counterpart device is set so that the polarization direction is orthogonal to the transmitted light. The light passes through and enters the beam splitter 25. Most of the received light is reflected by the beam splitter 25 and enters the end face of the receiving optical fiber (or light guide) 15. Part of the light passes through the beam splitter 25 and enters the optical position detection element 27.

  The beam splitter 25 is a flat plate in the conventional embodiments shown in FIGS. 4 to 7. In this embodiment, however, the beam splitter 25 is integrated with the polarizing beam splitter 22 as shown in FIG. Prism type.

  The light incident on the end face of the receiving optical fiber 15 is transmitted to a light detection element 26 such as an avalanche photodiode (APD) placed on a printed circuit board or the like at a location different from the separation optical system 11. Thus, a communication signal is received. A circuit for amplifying the received signal and a bias control circuit for the light detection element 26 are also located nearby.

  On the other hand, the signal from the optical position detection element 27 is processed by the control circuit 28 as angle correction information, and the drive signal is output to the drive circuit 29, as in the conventional embodiments of FIGS.

  The separation optical system 11 is fixed to a stage 12 and is driven on the stage 12 by an actuator 13 in two directions, a direction parallel to the paper surface and a direction perpendicular to the paper surface. (In FIG. 1, it is difficult to show a two-direction drive mechanism, so only one direction parallel to the paper surface is shown).

  Then, the actuator 13 is driven by the drive circuit 29 so that the position of the light spot 42 comes to the center of the light position detecting element 27 and the output of the four photodiodes 27a to 27d is all equal to each other. The position of the system 11 is driven and controlled. This is shown in FIGS. 2 (A) and 2 (B). It can be seen that the direction of the light beam for transmission / reception changes depending on the position of the optical system 11 with respect to the collimating optical system 10.

  Inside the separation optical system 11, the position of the optical position detection element 27, the end face of the transmission optical fiber 14, and the end face of the reception optical fiber 15 are all adjusted so that the optical axes coincide with each other. In the state where the light spot 32 hits the center, light is also incident on the center of the end face of the receiving optical fiber 15, and the center of the light from the end face of the transmitting optical fiber 14 radiates in the direction of the counterpart device. Is done.

  In this way, the optical axis deviation correction is performed so that the transmitted light is always in the direction of the received light, that is, the direction of the counterpart device.

  In this embodiment, the separation optical system 11 can be made compact and lightweight, and the peripheral circuit of the light-emitting element such as LD and the light-receiving element such as APD can be placed in another place to prevent an increase in weight. By connecting to the separation optical system 11, it is possible to drive the separation optical system 11 at a high speed with a light force while minimizing the connection of an electric cord or cable having a large weight or bending stress. As a result, even when the angle of the entire apparatus fluctuates at high speed due to disturbances such as vibration and wind pressure, the optical axis deviation correction can respond. Moreover, the size of the apparatus is not increased as in the conventional example of FIG. 6, and the cost is not increased due to the complicated lens configuration as in the conventional example of FIG. Rather, since the drive unit only needs to drive a small and light object, the required specifications of the drive unit are relaxed, which is advantageous in terms of cost. Since the light emitting element 21, the light receiving element 26 and their peripheral circuits 16, 17 can be arbitrarily arranged within the reach of the optical fiber, the degree of freedom in design layout is increased, which is advantageous for downsizing of the entire apparatus. In terms of electrical performance, measures against interference between transmitted and received signals and electrical disturbance noise can be easily achieved.

  (Only the optical position detecting element 27 and the peripheral circuit cannot detect the optical position by making light incident on the optical fiber, and thus are attached to the separation optical system 11 as usual and become electric cord wiring).

(Second embodiment)
A second embodiment according to the present invention is shown in FIG. In the embodiment of FIG. 3, the optical system that transmits and receives light is separated into a collimating optical system 10 and a separating optical system 11, and the separating optical system 11 is made compact and moves with a light force. 1 is the same as the embodiment of FIG. 1 in that it can be moved independently with respect to the collimating optical system 10.

  In the embodiment of FIG. 3, a light emitting element 21 such as a laser diode (LD) is attached to the separation optical system 11, and a transmission optical signal is directly output from the light emitting element 21. However, peripheral circuits such as a light emission control circuit and a modulation circuit are placed on a printed circuit board or the like at a place different from the separation optical system 11, and the light emitting element 11 and these circuits are provided with a minimum number of electric cords or cables ( For example, the transmission signal and the LD driving current are connected by a single coaxial cable).

  In the embodiment of FIG. 3, the light detection element 26 such as an avalanche photodiode (APD) is also attached to the separation optical system 11, and the received optical signal is directly incident on the light receiving surface of the light detection element 26. However, peripheral circuits such as a bias control circuit for the light detection element 26 and a circuit for amplifying the reception signal converted into an electric signal by the light detection element 26 are placed on a printed circuit board or the like at another location. These circuits are connected by a minimum number of electric cords or cables (for example, one coaxial cable on which a received signal and a bias voltage of a photodetecting element are superimposed).

  In this embodiment, only a light emitting element such as LD and a light receiving element such as APD, which are small and do not cause weight, are placed in the separation optical system 11, and each relatively large and heavy peripheral circuit is placed in another place. Thus, the separation optical system 11 is prevented from increasing in weight and can be reduced in size and weight, and the separation optical system 11 is driven at a high speed with a light force by minimizing the connection of an electric cord or cable having a large weight or bending stress. I can do it.

  The weight and bending stress of the electric cord and cable are slightly larger than those of the embodiment of FIG. 1 in which the transmission / reception signals are connected by optical fibers, and attention is paid to the electrical interference between the transmission / reception signals in the separation optical system 11 part. However, the configuration is simplified by the amount not passing through the optical fiber, and the cost can be made lower than that of the embodiment of FIG.

(Third embodiment)
In the first and second embodiments, the separating optical system 11 is moved in parallel with the collimating optical system 10 to change the direction of the transmission / reception light beam as shown in FIG. In this way, the direction of the transmission / reception light beam can be changed by rotating the separation optical system around a fulcrum. In the example of FIG. 8, the rotation is made around the point indicated by the mark ●. In this case, if the center of rotation is near the condensing point of the collimating optical system 10, the effect of changing the direction of the light beam is reduced. Therefore, a point slightly apart as shown in FIG.

(Fourth embodiment)
In the first to third embodiments, the purpose of moving the separation optical system 11 relative to the collimating optical system 10 is to correct the optical axis deviation by changing the direction of the light beam for transmission and reception. Therefore, the moving direction of the separation optical system 11 is perpendicular to the optical axis of the collimating optical system 10.

  However, in an optical space communication apparatus that performs communication using a light beam, not only control of the direction of the light beam but also control of the spread angle of the light beam is important. In order to transmit light power efficiently, an optical axis misalignment correction function is provided to reduce the divergence angle of the light beam, but there is a limit to narrowing the light beam, and the optical axis misalignment correction function It is necessary to keep it within the range of correction accuracy and response performance against disturbances such as vibration.

  Depending on the distance, the divergence angle of the light beam is controlled according to the distance by controlling the divergence angle to be large when the installation distance between the devices is short, and to decrease the divergence angle when the installation distance is long. Thus, a method of receiving an optical signal within the optimum optical reception intensity range is also effective.

  In the embodiment shown in FIG. 9, the moving direction of the separation optical system 11 can be moved not only in the direction perpendicular to the optical axis of the collimating optical system 10 but also in the direction of the optical axis. The spread angle can be changed. That is, the separation optical system 11 has a stage 92 having an actuator 93 that moves in the direction of the optical axis in addition to the stage 12 having the actuator 13, so that the separation optical system 11 not only in two directions perpendicular to the optical axis but also in the direction of the third optical axis. (In FIG. 9, it is difficult to show a drive mechanism in the direction perpendicular to the paper surface, so it is omitted). When the separation optical system 11 moves in the direction approaching the collimating optical system 10 by the actuator 93 and the stage 92, the divergence angle of the light beam increases. Conversely, when the separation optical system 11 moves away from the collimating optical system 10, the light beam The spread angle becomes smaller.

(Fifth embodiment)
In the first to fourth embodiments, the position of the separation optical system 11 with respect to the collimating optical system 10 is automatically moved, such as an optical space communication device having an optical axis deviation correction function. Changing the position of the separation optical system 11 relative to the optical system 10 and adjusting the direction and divergence angle of the light beam need not be limited to being performed automatically.

  For example, even for an inexpensive optical space communication device that does not have an automatic optical axis deviation correction function for short distances, etc., a method of driving the actuators 13, 93, etc. by manual switch operation, such as when adjusting the optical axis during assembly or installation. Can be considered. Further, the stages 12, 92, etc. have no actuator and may be a mechanism such as manual screw feeding. Even in such a case, the cost reduction effect by reducing the size of the periphery of the optical system and simplifying the adjustment mechanism in the optical axis direction is great.

First embodiment of the present invention A state in which the position of the separation optical system 11 is driven and controlled is shown. Second embodiment of the present invention Conventional example Example of spot position detection element Conventional example Conventional example Third embodiment of the present invention Fourth embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Collimating optical system 11 Separation optical system 21 Light emitting element 12, 92 Movable stage 13, 93 Actuator 14, 15 Optical fiber 16 Light emitting element peripheral circuit 17 Light receiving element peripheral circuit 18, 19 Coaxial code 22 Polarizing beam splitter 25 Beam splitter 26 Light receiving element 27 Spot Position Detection Element 28 Control Circuit 29 Drive Circuit

Claims (6)

An optical space communication device that is installed oppositely between remote points and performs communication using a light beam,
A first optical system for converting a divergent light beam into a light beam that is a substantially parallel light beam and sending it to a counterpart device, and for receiving a light beam that is a substantially parallel light beam from the counterpart device and converting it into a convergent light beam And a second optical system for separating the luminous flux sent to the counterpart device and the luminous flux received from the counterpart device, each on the same optical axis and having the opposite direction,
An optical space communication device comprising means for changing the relative position of the second optical system with respect to the first optical system (including not only translation but also change in angle). An optical space communication device that is installed oppositely between remote points and performs communication using a light beam,
A first optical system for converting a divergent light beam into a light beam that is a substantially parallel light beam and sending it to a counterpart device, and for receiving a light beam that is a substantially parallel light beam from the counterpart device and converting it into a convergent light beam And a second optical system for separating the luminous flux sent to the counterpart device and the luminous flux received from the counterpart device, each on the same optical axis and having the opposite direction,
Drive means for changing the relative position of the second optical system with respect to the first optical system (including not only translation but also angular change);
Angle detection means attached to the second optical system for detecting the angle of the light beam received from the counterpart device;
Based on the information from the angle detection means, the light beam transmitted to the counterpart apparatus is always controlled by controlling the drive means so that the angle of the light beam received from the counterpart apparatus becomes a predetermined value. An optical space communication device comprising control means for performing tracking control in a direction.   There is a light emitting element for generating an optical signal to be sent to the counterpart device, which is in a different place from the second optical system, and an optical waveguide (optical waveguide) is provided between the light emitting element and the second optical system. 3. The space optical communication apparatus according to claim 1, wherein the optical space communication apparatus is connected by a fiber, a light guide, or the like, and guides transmission light from the light emitting element to the second optical system through an optical waveguide.   There is an optical signal detection element for detecting an optical signal received from the counterpart device, which is in a different location from the second optical system, and between the optical signal detection element and the second optical system. The optical fiber is connected by an optical waveguide (optical fiber, light guide, etc.), and the received light from the second optical system is guided to the optical signal detection element by the optical waveguide. Optical space communication device.   The second optical system has a light emitting element for generating a light beam including an optical signal to be transmitted to the counterpart device, a circuit for controlling the light emission intensity of the light emitting element, and this light emission for generating an optical signal. The optical space communication apparatus according to claim 1, wherein the circuit that modulates the signal using a signal to be transmitted is placed at a location different from the second optical system. The second optical system has an optical signal detection element for detecting an optical signal included in a light beam received from the counterpart device, and a circuit for amplifying an electrical signal detected by the optical signal detection element is the first optical system. 3. The optical space communication apparatus according to claim 1, wherein the optical space communication apparatus is placed at a place different from the second optical system.

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